Pump with reciprocating high pressure seal and valve for vehicle braking systems

ABSTRACT

A pump assembly with a combination reciprocating high-pressure seal and fluid inlet check valve for use within brake systems. The pump assembly comprises a housing having a bore formed therethrough and a piston disposed within the bore for reciprocal movement therein. An annular seal is disposed around the piston for reciprocal movement thereon. The piston has at least one passageway formed therein. An inlet flange portion of the piston has at least one passageway formed therein. The passageway, the piston, and the annular seal cooperating to form a check valve assembly. The check valve assembly divides the bore into an inlet chamber and a pumping chamber. The annular seal is moveable to a first position relative to the piston in which the check valve assembly is in a flow-through position to fill the pump chamber with fluid from the inlet chamber during a fluid inlet stroke. The annular seal is moveable to a second position relative to the piston in which the check valve assembly is closed to pressurize the fluid within the pumping chamber during a pumping stroke.

BACKGROUND OF THE INVENTION

This invention relates in general to brake systems for vehicles and in particular to a pump assembly with a combination reciprocating high-pressure seal and fluid inlet check valve for use within brake systems.

In conventional vehicular brake systems having anti-lock brake, traction control and/or vehicle stability control, a supply of hydraulic fluid for the vehicle brakes is modulated by a hydraulic control unit. Various hydraulic pumps may be employed to selectively supply hydraulic fluid to the vehicle brakes. Several hydraulic pump designs are known.

U.S. Pat. No. 4,556,261 to Farr, discloses a prior art pump and skid sensing assembly for a vehicle hydraulic anti-skid braking system, as shown in FIGS. 1 and 2. The assembly comprises a housing 1 incorporating a hydraulic pump 2, and a solenoid-operated valve assembly 3. Only the operation of the pump 2 will be described herein, as the operation of the rest of the anti-skid braking system is not relevant to the present invention. The pump 2 includes a plunger 10, which reciprocates within a stepped bore 11 in the housing 1. The plunger 10 is engageable with a drive mechanism comprising a ring 12 rotatable on a shaft 4. The plunger 10 carries an ‘O’ ring seal 18 and a lip seal 19. The seals 18 and 19 are disposed on opposite sides of a passage 20 leading to the valve 3. The seals 18 and 19, the plunger 10, and the bore 11 define a chamber 22. A reservoir 35 supplies the chamber 22 with fluid.

The seal 19, which is illustrated in detail in FIG. 2, comprises an annular ring of elastomeric material, which is received in an annular groove 25 in the plunger 10. The groove 25 is parallel sided and is of an axial length greater than the thickness of the seal 19. Opposite faces 26 and 27 of the seal 19 are respectively planar and of reduced area, with the face 27 of reduced area being provided with at least one diametrical slot 28 which communicates with one or more passages 29 in the inner peripheral edge of the seal 19. The planar face 26 is adapted to seal against the adjacent, inner, face of the groove 25 to prevent flow from the secondary chamber 22 into the reservoir 35. The seal 19 is rather complex in that it contains at least one slot 28 and at least one passage 29 formed therethrough to control fluid flow through the seal 19.

As the plunger 10 is moved towards the ring 12, the seal 19 moves relative to the plunger 10 so that the face 26 is spaced apart from the adjacent face of the groove 25. This allows fluid from the reservoir 35 to be drawn into the increasing volume of the chamber 22 past the seal 19 with flow taking place through the slot 28 and the at least one passage 29 in the seal 19. As the plunger 10 is moved in the opposite direction, the face 26 of the seal 19 seals against the adjacent face of the groove 25 so that fluid cannot flow between the plunger 10 and the seal 19 or through the slot 28 and the at least one passage 29 within the seal 19. The seal 19 in this condition thus provides a seal between the plunger 10 and the wall of the bore 11, allowing the plunger 10 to pump fluid from the secondary chamber 22 into the primary chamber 23.

SUMMARY OF THE INVENTION

Although prior hydraulic pumps, such as the one described above, have been effective, it would be desirable to provide a low cost pump assembly having more easily manufactured and more durable components.

The present invention is a pump assembly with a combination reciprocating high-pressure seal and fluid inlet check valve for use within brake systems. The pump assembly comprises a piston for reciprocal movement within a bore in a housing.

The pump assembly includes a housing having a bore formed therethrough and a piston disposed within the bore for reciprocal movement therein. An annular seal is disposed around the piston for reciprocal movement thereon. The piston has at least one passageway formed therein. The passageway, the piston, and the annular seal cooperating to form a check valve assembly. The check valve assembly divides the bore into an inlet chamber and a pumping chamber. The annular seal is moveable to a first position relative to the piston in which said check valve assembly is in a flow-through position to fill the pumping chamber with fluid from the inlet chamber during a fluid inlet stroke. The annular seal is moveable to a second position relative to the piston in which the check valve assembly is closed to pressurize the fluid within the pumping chamber during a pumping stroke.

In a preferred embodiment, the piston includes a retaining flange, an inlet flange, and an intermediate portion disposed therebetween. Both the retaining flange and the inlet flange extend substantially perpendicular from the piston. The intermediate portion of the piston has at least one passageway formed therethrough. The retaining flange also has at least one passageway formed therethrough. The at least one passageway of the intermediate portion and the at least one passageway of the retaining flange are communicably connected. The inlet flange also has at least one passageway formed therethrough.

A high-pressure seal is disposed around the intermediate portion of the piston. The seal is not as thick as the intermediate portion is long, and, therefore, the seal can reciprocate between the retaining flange and inlet flange. The seal and the inlet flange cooperate to form a first check valve assembly, as will be described below.

The piston, housing, the first check valve assembly, and a second check valve assembly define a pumping chamber. The piston, housing, and the first check valve assembly define an inlet chamber. A fluid inlet supplies fluid to the inlet chamber.

On a fluid inlet stroke, the piston withdraws from the bore and the volume of the pumping chamber increases. As the piston withdraws, the seal is moved into a first position relative to the inlet flange, in which the seal is not seated against the inlet flange. With the seal in the first position, the first check valve assembly is opened, and fluid from the inlet chamber is allowed to flow into the pumping chamber.

On a pumping stroke, the piston moves toward the second check valve assembly, and the seal is moved into a second position relative to the inlet flange, in which the seal is seated against the inlet flange. When the seal is in the second position, the inlet flange and seal cooperate to prevent fluid from exiting the pumping chamber, such that the first check valve assembly is closed. The fluid pressure builds within the pumping chamber until the pressure overcomes the force required to unseat the ball of the second check valve assembly. The second check valve assembly then opens, allowing the pressurized fluid to exit the pumping chamber through a fluid outlet to be delivered to the vehicle brake system.

In an alternate embodiment of the invention, the at least one passageway in the retaining flange is communicably connected to at least one passageway in the seal. The seal and the inlet flange form a check valve assembly. When the seal is in the first position, fluid is allowed to flow through the at least one passageway in the inlet flange, below the seal, through the passageway in the seal, through the at least one passageway in the retaining flange, and into the pumping chamber. Thus, the check valve assembly is in a flow-through position. When the seal is in a second position, seated against the sealing surface of the inlet flange, the at least one passageway in the seal is prevented from communicating with the at least one passageway in the inlet flange. Thus, the check valve assembly is in a closed position.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a known prior art hydraulic pump assembly.

FIG. 2 is a cross sectional view of the seal of the known prior art hydraulic pump assembly illustrated in FIG. 1.

FIG. 3 is a prospective view of a first embodiment of a piston in accordance with the present invention.

FIG. 4 is a cross sectional view of the piston shown in FIG. 3, taken along line 4-4, with the piston disposed within a first embodiment of a pump assembly, in accordance with the present invention.

FIG. 5 is a cross sectional view of the pump assembly of FIG. 4.

FIG. 6 is an enlarged cross sectional view of a portion of a second embodiment of a pump assembly in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring again to the drawings, there is illustrated in FIG. 3, a first embodiment of a piston, indicated generally at 50, in accordance with this invention. The piston 50 comprises a shaft 51, a retaining flange 52, and an inlet flange 53. The retaining flange 52 extends substantially perpendicular from the shaft 51 at a first end portion 54 of the shaft 51. The inlet flange 53 extends substantially perpendicular from the shaft 51 below and spaced apart from the retaining flange 52. The retaining flange 52 and the inlet flange 53 cooperate to define an intermediate portion 55 of the shaft 51 disposed between retaining flange 52 and the inlet flange 53.

The shaft 51 is generally elongated along a longitudinal axis A. The shaft 51 includes a second end portion 56, opposite the first end portion 54. The intermediate portion 55, described above is disposed between the first end portion 54 and the second end portion 56. The second end portion 56 is engaged by a driving mechanism (not shown) for reciprocatingly driving the piston 50. The intermediate portion 55 of the shaft 51 may have a generally circular cross section. The intermediate portion 55 extends outwardly from the axis A to a radius R₁, as is shown in FIGS. 4 and 5, and as will be described further below. The intermediate portion 55 has at least one passageway 57 formed therethrough. In a preferred embodiment, the at least one passageway 57 comprises a plurality of longitudinally extending grooves, with preferably semi-circular cross-section, that have been machined through the intermediate portion 55 of the shaft 51 around the periphery of the intermediate portion 55. In a more preferred embodiment, the at least one passageway 57 comprises a plurality of longitudinally extending notches molded in the intermediate portion 55, with preferably rectangular or diamond-shaped cross-section. However, it will be appreciated that the at least one passageway 57 may be formed in the intermediate portion 55 in any manner, and may have any suitable cross-section. As used throughout the application, semi-circular encompasses any portion of a circle, which includes but is not limited to half of a circle. The at least one passageway 57 is formed through the intermediate portion 55 such that no part of the at least one passageway 57 extends further into the intermediate portion 55 than a radius R₂ from the axis A.

The retaining flange 52 may have a generally circular cross section, and has a radius taken from the axis A that is larger than the radius R₁ of the intermediate portion 55, the purpose of which will be described below. The retaining flange 52 has at least one passageway 58 formed therethrough. In a preferred embodiment, the at least one passageway 58 comprises a plurality of longitudinally extending grooves, preferably with semi-circular cross-section, that have been machined through the retaining flange 52 around the periphery of the retaining flange 52. In a more preferred embodiment, the at least one passageway 58 comprises a plurality of longitudinally extending notches molded in the retaining flange 52, with preferably rectangular or diamond-shaped cross-section. However, it will be appreciated that the at least one passageway 58 may be formed in the retaining flange 52 in any manner, and may have any suitable cross-section. It will also be appreciated that the retaining flange 52 may be any one of a plurality of nubs or tangs extending outwardly from said piston 50, the purpose of which will be described below. The at least one passageway 58 is formed through the retaining flange 52 such that the at least one passageway 58 does not extend into the retaining flange 52 any closer than a radius R₃ from the axis A as seen in FIG. 4. The radius R₃ is smaller than the radius R₁ of the intermediate portion, the such that the at least one passageway 58 is aligned to radially overlap the at least one passageway 57, and the at least one passageway 58 and the at least one passageway 57 are connected in fluid communication.

The inlet flange 53 may have a circular cross section, and has at least one passageway 59 formed therethrough. In a preferred embodiment, the at least one passageway 59 comprises a plurality of longitudinally extending grooves, preferably with semi-circular cross-section, that have been machined through the inlet flange 53 around the periphery of the inlet flange 53. In a more preferred embodiment, the at least one passageway 59 comprises a plurality of longitudinally extending notches molded in the inlet flange 53, with preferably rectangular or diamond-shaped cross-section. However, it will be appreciated that the at least one passageway 59 may be formed in the inlet flange 53 in any manner, and may have any suitable cross-section. The at least one passageway 59 is formed through the inlet flange 53 such that the at least one passageway 59 does not extend further into the inlet flange 53 any closer than a radius R₄ from the axis A, as seen in FIG. 4. The radius R₄ is greater than the radius R₁, the outer radius of the at least one passageway 57, such that even though the at least one passageway 57 and the passageway 59 may be aligned to overlap radially, the at least one passageway 57 and the at least one passageway 59 are not directly communicably connected with one another.

The piston 50 is suitable for use in a pump assembly, such as the first embodiment of a pump assembly, indicated generally at 60, in FIGS. 4 and 5. The pump assembly 60 comprises a housing 61 having a bore 62 formed therethrough. The piston 50 is mounted for reciprocal movement within the bore 62 of the housing 61. Preferably, the piston 50 is formed of a material that is sufficient to sustain operation of the pump assembly 60 under operating conditions within the pump assembly 60 as described herein, such as the relatively high operating pressures of a pump assembly within a vehicle brake system. Additionally, in a preferred embodiment, the piston 50 is comprised of materials that are compatible with hydraulic brake fluid.

An annular high-pressure seal 63 is disposed around the intermediate portion 55 of the piston 50. In a preferred embodiment, the high-pressure seal 63 has a generally rectangular radial cross section as illustrated for each portion of the seal 63 shown on either side of the axis A in FIG. 4. However, it will be appreciated that the seal may have any radial cross-section. In a preferred embodiment, the seal 63 is not as thick as the intermediate portion 55 is long, such that the seal 63 can reciprocate between the retaining flange 52 and the inlet flange 53 of the piston 50, as will be described below. The seal 63 is preferably elastomeric. In a preferred embodiment, the seal 63 includes a base material, such as Polytetrafluoroethylene (PTFE) sold under the tradename Teflon® and manufactured by DuPont, and a filler material, such as carbon. In a more preferred embodiment, the seal 63 includes carbon fiber, or other high tensile strength fibers suitable for use in composite materials. Preferably, the seal 63 is formed of a material that is sufficient to sustain operation of the pump assembly 60 under operating conditions within the pump assembly 60 as described herein, such as the relatively high operating pressures of a pump assembly within a vehicle brake system. In a preferred embodiment, the seal 63 is formed of a material that is sufficient to sustain operation of the pump assembly 60 with an operating pressure range of about 0 to about 250 bars absolute pressure within the pump assembly 60, as will be described in more detail below. However, it will be appreciated that operating pressure within the pump assembly 60 may vary, and may be a negative pressure under some operating conditions, as will be described below. In a preferred embodiment, the seal 63 is formed of a material that is sufficient to sustain operation of the pump assembly 60 in a temperature range of about −40 degrees Celsius to about 120 degrees Celsius. Additionally, in a preferred embodiment, the seal 63 is comprised of materials that are compatible with hydraulic brake fluid.

The seal 63 has a first surface 64 that slidingly engages the walls of the housing 61 that form the bore 62 to form a dynamic seal therebetween. The seal 63 also has a second surface 65 that slidingly engages the outer periphery of the intermediate portion 55 of the piston 50, although such is not required. The seal 63 is able to move relative to the intermediate portion 55 between a first position, in which the seal 63 contacts the retaining flange 52 and a second position, in which the seal 63 contacts the inlet flange 53 as will be described below. The second surface 65 may seal against only the outer periphery of the intermediate portion 55, and does not contact the inner periphery of the at least one passageway 57, such that the seal 63 does not enter the at least one passageway 57. Thus, no seal is formed between the seal 63 and the intermediate portion 55.

The seal 63 further includes a third surface 66 that engages a surface 68 of the retaining flange 52 when the seal 63 is in the first position thereof. As indicated above, in a preferred embodiment, the at least one passageway 58 is a plurality of similar passageways in the form of grooves that are symmetrically positioned around the retaining flange 52, so that the seal 63 is evenly axially supported by the retaining flange 52 when seated in the first position.

The seal 63 has a fourth surface 67 that may engage a sealing surface 69 of the inlet flange 53 when the seal 63 is in a second position relative to the inlet flange 53, as will be described below. When the seal 63 is in the second position, the fourth surface 67 engages the sealing surface 69. The seal 63 prevents fluid flow through the at least one passageway 59 through the inlet flange 53, because, as is best shown in FIG. 5, the seal 63 seats against the sealing surface 69 blocking the passageway 59. Fluid is not able to flow out of the at least one passageway 57 past the seal 63, so fluid is not able to flow from the at least one passageway 57, around the seal 63, and into the at least one passageway 59. Therefore, the seal 63, in the second position, prevents the at least one passageway 57 and the at least one passageway 59 from fluid communication with one another.

Thus, the seal 63 and the inlet flange 53 cooperate to form a first check valve assembly 70, as will be described in more detail below. In a preferred embodiment, the at least one passageway 59 is a plurality of similar passageways that are symmetrically positioned around the inlet flange 53, so that the seal 63 is evenly supported by the inlet flange 53 when seated in the second position.

The pump assembly 60 will now be further described. The second end portion 56 of the piston 50 is mounted so that the piston 50 may reciprocate within the bore 62 of the housing 61. The piston 50 slides against the walls of the bore 62 as the piston 50 reciprocates. A seal 71 may be provided or formed by the piston 50 and the walls of the bore 62. The seal 71, the seal 63, and the piston 50 define an inlet chamber 72 within the bore 62. A fluid inlet 73 is communicably connected to the inlet chamber 72 to supply fluid to the pump assembly 60, as will be described below. Alternatively, it will be appreciated that the seal 71 may not be provided, and the inlet chamber 72 may extend such that the fluid of the inlet chamber 72 may be used to lubricate the piston 50 and the walls of the bore 62 to facilitate the reciprocal movement therebetween. In a more preferred embodiment, an o-ring (not shown) may be disposed around the shaft 51 of the piston 50 near the second end portion 56 of the piston 50 instead of the seal 71 such that the inlet chamber 72 extends below the intersection of the walls of the bore 62 and the piston 50.

At the end of the bore 62 opposite the piston 50, a second check valve assembly 74 is provided. The second check valve assembly 74 includes a ball 75 and a seat 76. Preferably, the second check valve assembly 74 is formed of a material that is sufficient to sustain operation of the pump assembly 60 under operating conditions within the pump assembly 60 as described herein, such as the relatively high operating pressures of a pump assembly within a vehicle brake system. Additionally, in a preferred embodiment, second check valve assembly 74 is comprised of materials that are compatible with hydraulic brake fluid. A pumping chamber 77 is defined within the bore 62 between the second check valve assembly 74 and the combination of the piston 50 and the seal 63. As is evident from the structure of the pump 60 and as will be evident from the operation of the pump 60 described below, the pump 60 is highly efficient due to the relatively small unswept volume of the piston 50.

The operation of the pump assembly 60 will now be described. At the end of a pumping stroke, when the piston 50 is closest to the second check valve assembly 74, the seal 63 is in the second position, thereby seated against the sealing surface 69 of the inlet flange 53 (the first check valve assembly 70 is shut). During a fluid inlet stroke, the piston 50 moves away from the second check valve assembly 74. The seal 63 is disposed between the retaining flange 52 and the inlet flange 53, and, as the piston 50 moves away from the second check valve assembly 74, pressure in the pumping chamber 77 drops below the pressure in the inlet chamber 72 as the pumping chamber 77 expands. The differential pressure unseats the seal 63 from the inlet flange 53, opening the first check valve assembly 70 and allowing fluid to flow from the inlet chamber 72 through the passageways 59, 57, and 58, into the pumping chamber 77. The seal 63 will generally have greater friction to the wall of the bore 62 than to the piston 50, and will tend to remain stationary as the piston 50 moves. However, as the piston 50 continues to move away from the second check valve assembly 74, the retaining flange 52 will eventually intercept the seal 63, and the seal 63 will be drug away from the second check valve assembly 74 by the retaining flange 52 of the piston 50, so that the seal 63 is now in the first position thereof. Once the seal 63 has been intercepted by the retaining flange 52, the seal 63 will remain seated against the retaining flange 52 as long as the piston 50 continues to move in the same direction, e.g., away from the second check valve assembly 74.

During a pumping stroke, the piston 50 moves back toward the second check valve assembly 74. As the piston 50 moves, the seal 63 again tends to remain stationary due to friction with the wall of the bore. Additionally, as the pumping chamber gets smaller as the piston 50 moves toward the second check valve assembly 74, pressure starts to rise, even with the first check valve assembly 70 still open, due to head losses in the passageways. Thus, the seal 63 moves out of the second position thereof. As the piston 50 continues to move toward the second check valve assembly 74, the inlet flange 53 will eventually intercept the seal 63, and the seal 63 will be drug toward the second check valve assembly 74 by the inlet flange 53 of the piston 50. Once the seal 63 has been intercepted by the inlet flange 53, the seal 63 will remain in the second position thereof, i.e. seated against the inlet flange 53, as long as the piston 50 continues to move in the same direction, e.g., toward the second check valve assembly 74. When the seal 63 is in the second position thereof, the first check valve assembly 70 is in the closed position, as illustrated in FIG. 5. With the seal 63 seated against the sealing surface 69 of the inlet flange 53, fluid cannot flow into the at least one passageway 59 from the at least one passageway 57. Therefore, the pumping chamber 77 is isolated from the inlet chamber 72. Thus, as the piston 50 moves further into the bore 62, the volume of the pumping chamber 77 decreases, and pressure is raised in the fluid within the pumping chamber 77.

As the piston 50 continues to move toward the second check valve assembly 74, the fluid pressure within the chamber 77 continues to build until the fluid pressure within the chamber 77 is greater than the resistance required to unseat the ball 75 from the seat 76 of the second check valve assembly 74. When the ball 75 is unseated, the second check valve assembly 74 opens and pressurized fluid is discharged from the pump 60 via an outlet 78.

As the piston 50 continues to move toward the second check valve assembly 74, the volume of the inlet chamber 72 increases. The increase in volume of the inlet chamber 72 may create negative pressure or a vacuum pressure within the inlet chamber 72. This vacuum pressure within the inlet chamber 72 pulls fluid from the fluid inlet 73 into the inlet chamber 72. Thus, the pump assembly 60 may be a self-priming or pre-charging pump, and the pump assembly 60 may operate with negative pressure conditions within the inlet chamber 72. At the end of a pumping stroke, the first end portion 54 of the piston 50 is relatively close to the second check valve assembly 74. With the piston 50 in this position, the first check valve assembly 70 and the second check valve assembly 74 are in relatively close proximity to one another, such that the pumping chamber 77 is relatively small, as compared to the pumping chambers of conventional pumps. The axial distance between the first check valve assembly 70 and the second check valve assembly 74 is minimized so that the pump assembly 60 has a relatively small unswept volume.

It will be appreciated that the size and design of the seal 63, the at least one passageway 58 of the retaining flange 52, and the at least one passageway 59 of the inlet flange 53, must be coordinated so that the seal 63 and piston 50 cooperate such that the pump 60 operates as described above. Conversely, it will be appreciated that the seal 63, the at least one passageway 58 of the retaining flange 52, and the at least one passageway 59 of the inlet flange 53 could be any size or shape capable of performing as described above.

Referring now to FIG. 6, there is illustrated a portion of a second embodiment of a pump assembly, indicated generally at 160, in accordance with this invention. The pump assembly 160 is similar to the pump assembly 60, and only those elements that differ will be described herein, and corresponding elements have been given the same reference numeral incremented by 100.

The piston 150 includes a retaining flange 152, an inlet flange 153, and an intermediate portion 155 disposed therebetween. Unlike the intermediate portion 55 of the piston 50, the intermediate portion 155 of the piston 150 does not have a passageway formed therethrough. Instead, the intermediate portion 155 is preferably circular in cross-section, and is slidingly engaged by a seal 163. The seal 163 may reciprocate between the retaining flange 152 and the inlet flange 153, in a manner similar to that described above for the seal 63.

The seal 163 differs from the seal 63 in that the seal 163 has at least one passageway 180 formed therethrough. The at least one passageway 180 has an outer radius R₁ from the axis A. The outer radius R1 is smaller than the inner radius R₄ of the at least one passageway 159 in the inlet flange 153. The outer radius R₁ is larger than the inner radius R₃ of the at least one passageway 158 in the retaining flange 152.

The seal 163 and the inlet flange 153 form a check valve assembly 170. However, the structure of the check valve assembly 170 varies from structure of the check valve assembly 70. The at least one passageway 158 in the retaining flange 152 is communicably connected to the at least one passageway 180 in the seal 163. In a preferred embodiment, the at least one passageway 180 is a plurality of passageways sized such that no matter how the seal 163 is rotated relative to the retaining flange 152, the at least one passageway 180 is communicably connected to the at least one passageway 158 of the retaining flange 152, when the seal 163 is seated against the surface 168.

When the seal 163 is in a first position relative to the inlet flange 153, the seal 163 is unseated from the sealing surface 169 of the inlet flange 153, and may be seated against the surface 168 of the retaining flange 152, as described in the previous embodiment and as shown in FIG. 6. When the seal 163 is in the first position, fluid is allowed to flow through the at least one passageway 159, below the seal 163, through the passageway 180, through the at least one passageway 158, and into the pumping chamber 177. Thus, the check valve assembly 170 is in a flow-through position. When the seal 163 is in a second position, seated against the sealing surface 169 of the inlet flange 153, the at least one passageway 180 in the seal 163 is prevented from communicating with the at least one passageway 159. Thus, the check valve assembly 170 is in a closed position, such that the pump 160 works in a manner similar to that described for the pump 60.

The pistons 50, 150, seals 63, 163 and pump assemblies, 60, 160 have been described for use in a vehicle braking system, including, but not limited to, vehicle braking systems having anti-lock braking systems, and/or integrated or stand alone traction control and vehicle stability control systems. However, it will be appreciated that the pistons 50, 150, the seals 63, 163 and pump assemblies 60, 160 may be used in any vehicle component or in any other device requiring a piston, seal, or pump assembly. 

1. A pump apparatus comprising: a housing having a bore formed therethrough; a piston disposed within said bore for reciprocal movement therein; an annular seal disposed around said piston for reciprocal movement thereon, said piston having at least one passageway formed therein, said passageway, said piston, and said annular seal cooperating to form a check valve assembly, said check valve assembly dividing said bore into an inlet chamber and a pumping chamber, said annular seal being moveable to a first position relative to said piston in which said check valve assembly is in a flow-through position to fill said pump chamber with fluid from said inlet chamber during a fluid inlet stroke, said annular seal being moveable to a second position relative to said piston in which said check valve assembly is closed to pressurize the fluid within the pumping chamber during a pumping stroke; a fluid inlet communicably connected to said inlet chamber and adapted to supply said inlet chamber with fluid; and a fluid outlet communicably connected to said pumping chamber and adapted to release pressurized fluid from said pumping chamber.
 2. The pump apparatus of claim 1, wherein said piston has a longitudinal axis A and said piston comprises an inlet flange extending outwardly substantially perpendicular to said axis A, and wherein said at least one passageway in said piston comprises at least one longitudinally extending passageway formed in said inlet flange.
 3. The pump apparatus of claim 2, wherein said at least one passageway in said inlet flange is comprised of at least one longitudinally extending groove with semi-circular cross-section machined through said inlet flange.
 4. The pump apparatus of claim 3, wherein said at least one passageway in said inlet flange has an inner radius R₄ defined from said axis A that is larger than an inner radius of said seal defined from said axis A when said seal is centered about said axis A.
 5. The pump apparatus of claim 2, wherein said piston comprises a retaining flange, and wherein said at least one passageway in said piston further comprises at least one passageway formed in said retaining flange.
 6. The pump apparatus of claim 5, wherein said at least one passageway in said retaining flange is comprised of at least one groove with semi-circular cross-section machined through said retaining flange.
 7. The pump apparatus of claim 5, wherein said at least one passageway in said retaining flange has an inner radius R₃ defined from said axis A that is smaller than an inner radius of said seal defined from said axis A when said seal is centered about said axis A.
 8. The pump apparatus of claim 5, wherein said at least one passageway in said retaining flange and said at least one passageway in said inlet flange are communicably connected when said check valve assembly is in said flow-through position.
 9. The pump apparatus of claim 5, wherein an intermediate portion of said piston is disposed between said inlet flange and said retaining flange, said intermediate portion having at least one passageway formed therein, said at least one passageway in said piston further comprising said at least one passageway of said intermediate portion.
 10. The pump apparatus of claim 5, wherein said at least one passageway in said intermediate portion is comprised of at least one groove with semi-circular cross-section machined through said intermediate portion.
 11. The pump apparatus of claim 10, wherein said at least one passageway in said intermediate portion, said at least one passageway in said inlet flange, and said at least one passageway in said retaining flange are communicably connected when said check valve assembly is in said flow-through position.
 12. The pump apparatus of claim 10, wherein said at least one passageway in said intermediate portion has an outer radius R₁ defined from said axis A that is smaller than an inner radius R₄ of said at least one passageway in said inlet flange defined from said axis A.
 13. The pump apparatus of claim 5, wherein said seal includes at least one passageway formed therein, said at least one passageway in said seal and said at least one passageway in said piston are communicably connected when said check valve assembly is in said flow-through position.
 14. The pump apparatus of claim 13, wherein said at least one passageway in said seal has an outer radius defined from said axis A that is smaller than an inner radius R₄ of said at least one passageway in said inlet flange defined from said axis A.
 15. A pump apparatus comprising: a housing having a bore formed therethrough; a piston disposed within said bore for reciprocal movement therein; an inlet flange, said inlet flange extending outwardly from said piston, said inlet flange having at least one passageway formed therein; a retaining flange, said retaining flange extending outwardly from said piston, said retaining flange having at least one passageway formed therein; an intermediate portion, said intermediate portion disposed between said inlet flange and said retaining flange, said intermediate portion having at least one passageway formed therein, said at least one passageway formed in said retaining flange being communicable with said at least one passageway formed in said intermediate portion of said piston; an annular seal disposed around said intermediate portion of said piston, said seal slidingly engaging the walls of said bore, said seal and said piston cooperating to form a check valve assembly, said bore being divided into an inlet chamber and a pumping chamber by said check valve assembly, said seal being moveable to a first position spaced apart from said inlet flange such that said check valve assembly is in a flow-through position to allow fluid to fill the pumping chamber, said seal being moveable to a second position sealing against said inlet flange such that said check valve assembly is in a closed position to allow fluid within said pumping chamber to be pressurized during movement of said piston in a pumping stroke; a fluid inlet communicably connected to said inlet chamber and adapted to supply said inlet chamber with fluid; and a fluid outlet communicably connected to said pumping chamber and adapted to release pressurized fluid from said pumping chamber.
 16. The pump apparatus of claim 15, wherein said at least one passageway in said inlet flange is comprised of at least one groove with semi-circular cross-section machined through said inlet flange.
 17. The pump apparatus of claim 15, wherein said at least one passageway in said retaining flange is at least one groove with semi-circular cross-section machined through said retaining flange.
 18. The pump apparatus of claim 15, wherein said annular seal is comprised of at least one of Polytetrafluoroethylene and Carbon Fiber.
 19. The pump apparatus of claim 15, wherein said check valve is in the closed position when said seal is seating on said inlet flange.
 20. A piston and seal assembly for a vehicle braking system pump comprising: a piston having an inlet flange, a retaining flange, and an intermediate portion disposed between said inlet flange and said retaining flange, said intermediate portion having at least one passageway formed therein, said inlet flange having at least one passageway formed therein, said retaining flange having at least one passageway formed therein, said at least one passageway formed in said retaining flange being communicable with said at least one passageway formed in said intermediate portion of said piston; and an annular seal disposed around said intermediate portion of said piston, said seal and said piston cooperating to form a first check valve assembly, said seal being moveable to a first position relative to said inlet flange in which said first check valve assembly is in a flow-through position, said seal being moveable to a second position relative to said inlet flange in which said first check valve assembly is in a closed position.
 21. A pump comprising: a housing having a bore formed therethrough; a piston disposed within said bore for reciprocal movement therein, said piston having an inlet flange, a retaining flange, and an intermediate portion disposed between said inlet flange and said retaining flange, said inlet flange having at least one passageway formed therein, said retaining flange having at least one passageway formed therein; an annular seal disposed around said intermediate portion of said piston, said seal and said inlet flange cooperating to divide said bore into an inlet chamber and a pumping chamber; a fluid inlet communicably connected to said inlet chamber, said seal being moveable to a first position relative to said inlet flange from said inlet chamber to permit fluid communication between said at least one passageway in said inlet flange and said at least one passageway in said retaining flange to allow fluid to fill said pumping chamber from said inlet chamber; and a fluid outlet communicably connected to said pumping chamber to release pressurized fluid from said pumping chamber, said seal being moveable to a second position relative to said inlet flange in which said seal contacts said at least one passageway in said inlet flange to prevent fluid communication between said at least one passageway in said inlet flange and said at least one passageway in said retaining flange such that fluid within said pumping chamber is pressurized by movement of said piston during a pumping stroke and released through said fluid outlet.
 22. A pump for a vehicle braking system comprising: a housing having a bore formed therethrough; a piston disposed within said bore for reciprocal movement therein, said piston defining a longitudinal axis, said piston having an inlet flange, a retaining flange, and an intermediate portion disposed between said inlet flange and said retaining flange, said inlet flange having a plurality of longitudinally extending grooves with semi-circular cross-section formed in a radially outer surface thereof, said intermediate portion having a plurality of longitudinally extending grooves with semi-circular cross-section formed in a radially outer surface thereof, said plurality of grooves in said intermediate portion being communicably connected to said plurality of grooves in said inlet flange, said retaining flange having a plurality of longitudinally extending grooves with semi-circular cross-section formed in a radially outer surface thereof, said piston being comprised of materials compatible with hydraulic brake fluid and adapted to withstand differential pressure consistent with use in a vehicle brake system; an annular seal disposed around said intermediate portion of said piston, said seal and said intermediate portion cooperating to divide said bore into an inlet chamber and a pumping chamber, said seal being comprised of materials compatible with hydraulic brake fluid and adapted to withstand differential pressure consistent with use in a vehicle brake system; a fluid inlet communicably connected to said inlet chamber to supply said inlet chamber with fluid, said seal being moveable to a first position relative to said inlet flange in which said plurality of grooves in said inlet flange are communicably connected to said pumping chamber, such that fluid from said inlet chamber fills said pumping chamber; a fluid outlet communicably connected to said pumping chamber; and a check valve disposed within said fluid outlet, said check valve being normally closed, said seal being moveable to a second position relative to said inlet flange in which said plurality of grooves in said inlet flange are prevented from communicating with said pumping chamber, such that the pressure of the fluid within the pumping chamber builds until said check valve opens and pressurized fluid is released from said pumping chamber through said fluid outlet, said check valve being comprised of materials compatible with hydraulic brake fluid and adapted to withstand differential pressure consistent with use in a vehicle brake system; 